slow speed upload

Hi guys
I am using mikrotik CCR2116-12G-4S+ and CRS326 24G-2S+,. i have 2 line WAN (400Mb download and 400Mb upload)
I config vlan-trunking , everything is ok in 1 years, but near here time, upload is very slow (50Mb), download is ok,
But when I turn off vlan, upload is 400Mb.
Does anyone have any idea why is this happening?
i m sorry, my English is not good